Better handle the arguments common to all MI commands.

Summary:
I observed that eclipse was passing --thread-group for many other commands
then we are currently handling. Looking at the MI documentation, the
following link states that each MI command accept the --thread and
--frame option. Looking at the GDB implementation, it seems that apart
from these 2, --thread-group is also handled the same way.

https://sourceware.org/gdb/onlinedocs/gdb/Context-management.html#Context-management

So instead of handling those arguments in every comamnds, I have moved
them into the base class and removed them from elsewhere. Now any command
can use these arguments. The patch seems big but most of the changes are
mechanical.

Reviewers: ki.stfu

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D14177

llvm-svn: 251636