Fixed location of const
Merge pull request #145 from ChrisNisbet01/drv_timer_const_fix

Minor 'const' issue.
making it really const this time.
CN - Changes to drv_timer.c to reduce time spent in the interrupt handler.
CN - Change so that the EXTI interrupt is cleared at the beginning of the handler rather than at the end.
CN - Changes to mixTable() so that some calculations of motor[] values are only performed if the device is armed. Previously the values were always calculated, and then overridden if the device was not armed.
CN - Ignore some Source Insight files.
CN - More files to ignore.
CN - More files to ignore.
CN - More tidying of drv_timer.c.
Although the original intention was for the timers[] array to be const, and therefore held in ROM, the const was in the wrong place, meaning that that array was still in RAM.
Made some more changes to timers[] so that it is less likely for future errors to occur should this table ever be altered. Using designated initialisers, which is a C99 thing, so I'm not too sur if the authors will be happy about that, but for now, I'll keep things like this.
CN - More tidying of drv_timer.c.
Replaced referenced to 'uint' (non-standard apparently) with plain old int and unsigned int.