Make the name field in projects optional (#870)

Closes #858.

If a project is named `default.project.json`, it acts as an `init` file
and gains the name of the folder it's inside of. If it is named
something other than `default.project.json`, it gains the name of the
file with `.project.json` trimmed off. So e.g. `foo.project.json`
becomes `foo`.

rojo-test/serve-test-snapshots/end_to_end__tests__serve__no_name_default_project_all.snap

@@ -0,0 +1,39 @@
+---
+source: tests/tests/serve.rs
+expression: "read_response.intern_and_redact(&mut redactions, root_id)"
+---
+instances:
+  id-2:
+    Children:
+      - id-3
+    ClassName: Folder
+    Id: id-2
+    Metadata:
+      ignoreUnknownInstances: true
+    Name: top-level
+    Parent: "00000000000000000000000000000000"
+    Properties: {}
+  id-3:
+    Children:
+      - id-4
+    ClassName: Folder
+    Id: id-3
+    Metadata:
+      ignoreUnknownInstances: false
+    Name: second-level
+    Parent: id-2
+    Properties: {}
+  id-4:
+    Children: []
+    ClassName: IntValue
+    Id: id-4
+    Metadata:
+      ignoreUnknownInstances: true
+    Name: third-level
+    Parent: id-3
+    Properties:
+      Value:
+        Int64: 1337
+messageCursor: 0
+sessionId: id-1
+

rojo-test/serve-test-snapshots/end_to_end__tests__serve__no_name_default_project_info.snap

@@ -0,0 +1,14 @@
+---
+source: tests/tests/serve.rs
+assertion_line: 316
+expression: redactions.redacted_yaml(info)
+---
+expectedPlaceIds: ~
+gameId: ~
+placeId: ~
+projectName: top-level
+protocolVersion: 4
+rootInstanceId: id-2
+serverVersion: "[server-version]"
+sessionId: id-1
+

rojo-test/serve-test-snapshots/end_to_end__tests__serve__no_name_project_all.snap

@@ -0,0 +1,40 @@
+---
+source: tests/tests/serve.rs
+assertion_line: 338
+expression: "read_response.intern_and_redact(&mut redactions, root_id)"
+---
+instances:
+  id-2:
+    Children:
+      - id-3
+    ClassName: Folder
+    Id: id-2
+    Metadata:
+      ignoreUnknownInstances: true
+    Name: no_name_project
+    Parent: "00000000000000000000000000000000"
+    Properties: {}
+  id-3:
+    Children:
+      - id-4
+    ClassName: Folder
+    Id: id-3
+    Metadata:
+      ignoreUnknownInstances: false
+    Name: second-level
+    Parent: id-2
+    Properties: {}
+  id-4:
+    Children: []
+    ClassName: BoolValue
+    Id: id-4
+    Metadata:
+      ignoreUnknownInstances: true
+    Name: bool_value
+    Parent: id-3
+    Properties:
+      Value:
+        Bool: true
+messageCursor: 0
+sessionId: id-1
+

rojo-test/serve-test-snapshots/end_to_end__tests__serve__no_name_project_info.snap

@@ -0,0 +1,14 @@
+---
+source: tests/tests/serve.rs
+assertion_line: 335
+expression: redactions.redacted_yaml(info)
+---
+expectedPlaceIds: ~
+gameId: ~
+placeId: ~
+projectName: no_name_project
+protocolVersion: 4
+rootInstanceId: id-2
+serverVersion: "[server-version]"
+sessionId: id-1
+

rojo-test/serve-test-snapshots/end_to_end__tests__serve__no_name_top_level_project_all.snap

@@ -0,0 +1,20 @@
+---
+source: tests/tests/serve.rs
+assertion_line: 357
+expression: "read_response.intern_and_redact(&mut redactions, root_id)"
+---
+instances:
+  id-2:
+    Children: []
+    ClassName: StringValue
+    Id: id-2
+    Metadata:
+      ignoreUnknownInstances: true
+    Name: no_name_top_level_project
+    Parent: "00000000000000000000000000000000"
+    Properties:
+      Value:
+        String: "If this isn't named `no_name_top_level_project`, something went wrong!"
+messageCursor: 0
+sessionId: id-1
+

rojo-test/serve-test-snapshots/end_to_end__tests__serve__no_name_top_level_project_info.snap

@@ -0,0 +1,14 @@
+---
+source: tests/tests/serve.rs
+assertion_line: 351
+expression: redactions.redacted_yaml(info)
+---
+expectedPlaceIds: ~
+gameId: ~
+placeId: ~
+projectName: no_name_top_level_project
+protocolVersion: 4
+rootInstanceId: id-2
+serverVersion: "[server-version]"
+sessionId: id-1
+