Bug fixes and prevent play mode on compile errors

• 754b59b: Now prevent the user from entering play mode in editor if there are any compile errors in their U# scripts to imitate how Unity acts with normal C# scripts.
• 754b59b: Add option to settings menu to only compile scripts when Unity is focused.
• 06a70d3: Fix to allow empty statements such as while(conditionFunc()) ;, reported by @phi16
• 06a70d3: Allow + prefix unary operator which is an identity operation that doesn't do anything, but can be used for code clarity, reported by @phi16
• 06a70d3: Update an error about multidimensional and jagged arrays to be accurate to the current support for jagged arrays, but not multidimensional arrays. Reported by @phi16
• 06a70d3: Fix to allow empty conditions on for loops
• 06a70d3: Prevent compile from progressing if an error is hit while building class definitions, reported by @VowganDesign
• 06a70d3: Add better coverage on errors for invalid name, and fix some cases where the name was not being propagated correctly, reported by @phi16