Made Launchpad sample operational (partially)

Launchpad sample now works, but with incorrect timing. Timer clock
source switched to submaster clock and interrupt enable switched to
TA0CCR0. Debug flags also enabled for use with GDB on target.
Timers with different bit-widths, fast clocks.

Added implementation and tests for timers with clocks sources too fast
to count a single millisecond (the smallest unit of time we support) in
one cycle. The driver currently refuses to support these scenarios,
though they should be later. Support and tests for timers with different
counting ranges was also added.
Updated samples' system definitions.

Updated TargetSystem headers for both the Trinket and Launchpad samples
to match latest TimerDriver version. Both are confirmed working on
hardware, though the Launchpad sample still has the wrong timing.