Documentation and a bit of cleanup.

Added documentation for non-trivial logic in Contexts, Phases and
TreeTransforms.
Removed redundant vars and casts
Fix TypeTestCasts

def p() = println().isInstanceOf[Long & Int]

was rewritten to

val ev$1: [T0]Boolean(x.isInstanceOf) = println().isInstanceOf
println().$isInstanceOf[Long & Int].&&(println().$isInstanceOf[Long & Int])
Intercepted methods transformer

    Replace member references for:
    methods inside Any( == and !=)
    ## on primitives
    .getClass on primitives
move InfoString from ErrorReporting to Decorators and

remove all isSensical/SuppressedMessage logic from InfoString
remove var ContextBase.suppressNonSensicalErrors, and

decouple Diagnostic from ContextBase
add d string interpolator (marks nonsensical error messages)
remove SuppressedMessage exception and update Diagnostic as needed
replace i"..." by d"..." if string might go into a

Diagnostic and might be nonsensical

Conflicts:
	src/dotty/tools/dotc/typer/Checking.scala
	src/dotty/tools/dotc/typer/TypeAssigner.scala
replace some s"..." by i"..."

Conflicts:
	src/dotty/tools/dotc/typer/TypeAssigner.scala
fix: isSensical in d"..." impl must inspect contents of List arg
fix: do not count suppressed messages for summary
Merge pull request #103 from DarkDimius/transform/erasure-transforms

TypeTestCasts fixes and InterceptedMethods transformer
Merge pull request #105 from DarkDimius/docs

Documentation and a bit of cleanup.
Reduce verbosity of logs.

We are already over limit on output size imposed by travis that is shown
in webpage, if we'll continue to add tests will be soon over limit even
to run builds.
This commit disables printing of classpath, and removes printlns in
several places.
In order for ShowClassTests to print info as is was printing
previously, please set "test.ShowClassTests.verbose" property.
Make transforms loggable

using traceIndented in the transform method.
test for allOverriddenSymbols

... to verify whether they work correctly.
Merge pull request #112 from dotty-staging/topic/loggable-transforms

Topic/loggable transforms
Merge pull request #99 from samuelgruetter/infostring2

Error reporting improvements
Merge pull request #110 from DarkDimius/silence

Reduce verbosity of logs.
Install method for SymDenotations

Add a new method to install a SymDenotation after a specific
phase has run. The new denotation replaces the current denotation
of the symbol starting with the period after the given phase.