Remove Generic Exceptions

[ehennenfent]

We use raise Exception in 47 different places. Not all of those are in unit tests. As a general rule, we should change these to more-specific exceptions so that it's easier to catch specific issues.

[disconnect3d]

There are only 5 places left after #1537, not taking into account examples/tests/tests generators:

➜  manticore git:(master) ✗ git grep 'raise Exception' | grep -v examples | grep -v test_ | grep -v make_tests | grep 'raise Exception'
manticore/core/manticore.py:973:                    raise Exception("Deadlock: Waiting for CTRL+C")
manticore/core/plugin.py:129:            raise Exception
manticore/ethereum/cli.py:61:                    raise Exception(
manticore/platforms/decree.py:283:                raise Exception("Set_brk can never work. avoid overflows")
manticore/utils/helpers.py:88:                raise Exception(

And taking everything else into account its 15:

➜  manticore git:(master) ✗ git grep 'raise Exception' | wc -l
      15