Patch the dev tools to disable the cache

See adobe/brackets#2732 -  If the cache is disabled via the remote debugging protocol, only the next reload is guaranteed to not be cached (regardless of whether it occurs while the client is still connected or not). Also, all reloads during that connection will not be cached. But if there has been a reload after disabling the cache while still connected, the first reload after having disconnected will **not** be cached.

So we need to disable the cache after every reload. Normally the dev tools don't do that. They disable the cache once when you open them (and every time you check the checkbox).

The script to patch dev tools is run after downloading CEF, but can be re-run later.

Procedure:
- The PAK ID for devtools.js (currently 20501) is extracted from `include/cef_pack_resources.h`
- For both Release and Debug, devtools_resources.pak is backed up as devtools_resources.pak.bak
- devtools_resources.pak.bak gets unpacked to devtools_resources
- devtools_resourcs/20501 gets patched in three places (the checkbox to disable the cache is checked by default, and the call to NetworkAgent.setCacheDisabled(true); now happens on every reload, not just once)
- devtools_resources gets packed as devtools_resources.pak

This may not be compatible with all future versions of the dev tools, but I made the string searches somewhat flexible. Potentially we are good for a while.