Handle bp.cmd and RBreakpointItem->cmd in RDebugContinue (bps and traces)

- Add scr.echo
Bring back asm.trace and dbg.trace to life
Fix #1593 - r2 -cr -- segfault
Add usage for p6*, p6e, p6d (defaults to core->blocksize)
Add pae?, pad? usage
Add support of RBuffer instead of FILE

use r_buf_seek and r_buf_read
Fix nested struct output
Add timestamp support in pf
Add timestamp
Fix #1603 - Sj is an alias for iSj.

- Fix a typo in the 'wt' command
Fix previous 'wt' commit and disable #! in sandbox mode (Fix #1604)
Add pwd usage
Fix pf
Improve linked list display in pf
Add pfs to print struct size
Initial implementation of the & command. Bump capstone
Add missing file
More fixes for the &Task command
Simplify code to fix COV 1250448
Fix COV#1250308 and COV#1250307