Update install-sx.sh

Made the install script multi-OS friendly, and also added some compilation tips for less experienced users.
clarify error message
Add libobelisk CFLAGS to AM_CPPFLAGS

This fixes a build failure when libobelisk is installed in a non-standard location.
update instructions.
use renamed raw_data_script (was coinbase_script)

corresponds to libbitcoin change:
rename coinbase_script() to raw_data_script()
https://github.com/spesmilo/libbitcoin/commit/f7d7f75ec75c5c0dfc4af2c77a4e2ee2e7369f3b
updated outdated links.
Change all instances of "http://github.com/genjix/sx/" to "http://github.com/spesmilo/sx/".

Also edited cheatsheet.svg to fit new URL.

NOTE: cheatsheet.png has old URL - couldn't figure out how to export it
nicely.
Merge pull request #7 from veox/master

Update documentation with new repo link
fix order of magnitude error in mktx usage
Merge pull request #10 from ryancdotorg/patch-2

fix order of magnitude error in mktx usage
Fixed cpu usage bug where floating point values inside sleep are rounded down to 0.

Replaced sleep(0.1) to msleep(100)

Thanks to AgentME
msleep -> usleep
changed to usleep in history.cpp
install-sx workaround for libconfig++8-dev packages.
additional update.
organise commands into categories (thanks to tphyahoo from Freenode IRC)
remove debug line.
added libwallet to sx. functionality from libbitcoin that is not core will be forked into libwallet from now on.
fix compile errors due to libwallet port.
"most commonly used commands" -> "commands" since it's a full list.