Stepwise functions - parity with strudel

[yaxu]

In strudel

• pace
• stepcat
• stepalt
• expand
• contract
• extend
• take - steptake due to prelude clash Overriding take and drop .. or making a tidal prelude? #1144
• drop - stepdrop due to prelude clash Overriding take and drop .. or making a tidal prelude? #1144
• polymeter
• shrink
• grow
• tour
• zip

Not in strudel

• stepwhile
• nth
• nthcycle
• stepevery
• stepeverycycle