Only show first overload in a series of consecutive overload signatures for navigateTo
Finished up "overload collapsing" for navigate-to.

Current semantics:
  - If an overload lacks an implementation, go to the first implementation.
  - If an overload has any implementation, go to the first one.
  - If there are any declarations between an implementation and any overload, this will split the series of overloads (note that this is invalid code).
Initial implementation of Union Types
Add assserts to help diagnose signature help crash #832
Narrowing of variable types using typeof/instanceof type guards
Merge pull request #804 from Microsoft/overwhelmedByOverloads

Only show first overload in a series of consecutive overload signatures
Merge branch 'master' into sigHelpCrash
Merge pull request #848 from Microsoft/sigHelpCrash

Add asserts to help diagnose signature help crash #832
add declaration target to generate declarations for compiler and services
Addressing CR feedback
Accepting new baselines

The new baselines all look correct to me, but obviously a number of the
tests need to be updated to reflect union types and the new behavior of
best common type. This commit does not cover that.
Improved type argument inference with union types
Merge branch 'master' into unionTypes
Accepting new baselines after merge with master

The tuple type tests from master need to be updated to reflect the new
best common type behavior from union types. This commit simply accepts
the baselines as they are.
Merge branch 'unionTypes' into prim_type

Conflicts:
	src/compiler/types.ts