Cleaned up many error codes. For any who is filling in error strings into

lldb_private::Error objects the rules are:
- short strings that don't start with a capitol letter unless the name is a
  class or anything else that is always capitolized
- no trailing newline character
- should be one line if possible

Implemented a first pass at adding "--gdb-format" support to anything that
accepts format with optional size/count.

llvm-svn: 142999