Bugfix for KLxx/K20 pwm period

Period is MOD + 1, so needs to add/substract 1 in the correct places
Merge branch 'master' of https://github.com/Sissors/mbed into Sissors-master
Merge branch 'Sissors-master'
Merge branch 'master' of https://github.com/mbedmicro/mbed
moved PeripheralNames.h to target folder (set new target values to 0)
Moved peripheral PinMap declarations to PeripheralPins.c
Deleted duplicate mbed_overrides.c