Add flag to ignore pre- and post-hooks

Adds the ability to specify on the command line that pre-hooks
(--ignore-pre-hooks), post-hooks (--ignore-post-hooks), or both
(--ignore-hooks) should be ignored.

This can be useful when a hook is expensive to execute, and not needed for every compile or clean. For example, having relx as a post-compile hook, to create a release, which isn't needed when doing compiles during development.

Otherwise, one's rebar.config could be manually modified to remove the hooks until they're needed again, or a copy of the rebar.config could be maintained, without the hook, but those both require extra work.

Separate makefile targets can include or not include an --ignore-* flag. For example "make dev" can invoke "rebar --ignore-post-hooks compile", while "make release" can invoke "rebar compile" (to allow the normal hook execution).

inttest/thooks_exclude has been added to test this (based on the existing inttest/thooks)

No additional Dialyzer warnings are generated from these changes ("make check" on the current master results in about 15 warnings, however).