1) Fixed all incorrect ticks-->ms and ms-->ticks conversions
2) Replaced conversions by macro. Strict usage of this macro
will prevent errors of this type.
Changes requested in review.
Merge pull request #772 from kubark42/port-tick-fixes

Replace all * portTICK_RATE_MS and /portTICK_RATE_MS by MS2TICKS and TICKS2MS macros