Add switches to skip and ignore checkstyle.

This should probably go to airbase in the long run. This allows a
submodule to set air.check.fail-checkstyle to false for development,
therefore no longer need to constantly reformat and optimize the code
while developing.
Fix some warnings flagged by Eclipse.

static member access
overriding varargs with []

Closes #1411
Add lag and lead window functions
Control cassandra client timeouts

Closes #1435
Generate filter/project methods only with required arguments

The compiler was previously generating them with all inputs across all filters and
projections as arguments, regardless of whether they were needed in the method body
Minor cleanup in ExpressionKey

Reuse SubExpressionExtractor and make code more readable