Multithread compile tasks

• #36: Multithread compile tasks for each module. On larger projects this can speed up compiles significantly.
• 3a20b64: Add support for nameof expression, requested by @orels1 #34
• aa9b912: Prevent readonly and const fields from being settable in the inspectors, reported by @mkc1370
• d3e9cc4: Fix casts from object to string that were creating an empty string instead of return null, reported by @naqtn #32
• eb269d7: Fix casts propagating incorrect types when chained together, reported by lamp