dont add gettext paths/domains twice

having the same path multiple times in a boost locale generator slows
down generate() significantly.
update the locale lazily

Updating it whenever we add a new messages path or domain could have a
bad performance.
fix convert old saves

This fixes loading start of scenario saves form 1.10.x

We also use clear_children instead of remove_child to work around  a bug
with config::remove_child and config::has_child : if we remove all of
the configs childs with remove_child then has_child still returns true.
move six game_events fcns to be methods of manager

In preparation for manager to become a non-singleton class
make the game_events::manager not a singleton class

moves all of the static, filescope variables to be member variables
of the manager
split game_events::manager code into separate files
refactor game_events::context

- Move the implementation details out of header
- Use standard C++ data structures
make game_events::pump not a singleton

Instances of this are now owned by the manager.

It would be nice to refactor this to provide all of the front-
facing methods in the manager instead of in the pump, since the
pump itself is somewhat an implementation detail. But this is
nearly the "smallest" diff change that would remove the singleton
restriction.
fix gcc build: rename class game_events::pump -> t_pump
travis: enable x2 build parallelism

Travis claims the linux build environment has two cores available,
this is an experiment to see if jobs=2 improves the build time.
Updated codeblocks projectfile with files from aff3cb8da5ec

Codeblocks also changed all forward slashes to backslashes
Use utf8 arrows instead of < > for help Back/Forward buttons