PostProcessors timeout

[proArtex]

Q	A
Bug Report?	no
Feature Request?	no
BC Break Report?	no
RFC?	yes
Imagine Bundle Version	2.0

OptiPngPostProcessor creates and runs new Process($processArguments) in processWithConfiguration() method, but it doesn't contain 4th argument $timeout in constructor, so it becomes 60s by default. This postprocessor may take over 60s, so it would be great to have ability to configure timeout of processors in some way.

[robfrawley]

This is already in the works in #993. We'll see if we can't get it in the 2.0.0 release. If you want to discuss any specifics about implementations, please continue the discussion there: #993.