suport for every other/third minute, etc

[leonardodino]

using an expression like:

*/2 * * * *

results in:

Every 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56 and 58th minute past every hour

the result shoud be more readable, like:

"every other minute" for */2 * * * *

or

"every forth hour" for 0 */4 * * *