disasm fixes, fix backward disasembly, make pdj not behave as pDj

- disasm indentation fixes
- fix backward disassembly. See differences:
   before: http://pastebin.com/bViwKDwT
   after: http://pastebin.com/yXPnfeBE
- pdj was stopping at block size number of bytes, so if more opcodes were requested, it only returned the opcodes in the first block size bytes
- webui improvements:
   - preload of instructions when clicking on instructions close to start or end
   - highlight all var accesses when clicking on one of them