allow hd-pub to be used to convert a private key to a public one.
normalise error messages for hd-pub
patch by Wolf0 (bitcointalk) for install-sx to work for Arch.
hd-seed: generate proper extended private key version byte when using testnet.

Achieved by using a new configuration variable `testnet` in sx.cfg, can
be set to "true" or "false" (string).

Drawback: need to include libobelisk_LIBS when building.
hd-seed: narrow build dependency to libconfig++.
config: add `testnet`, default to `false`.
update for latest stealth changes.
comment fetch_history() from sx monitor command
Merge pull request #75 from veox/hd-seed-valid-testnet

hd-seed: proper version bytes for testnet
sx monitor by binary prefix instead of by address now.
doc: obworker has been renamed to obelisk-server.
add subcategories to help file and make other improvements to usability
Merge pull request #78 from tphyahoo/develop-helpfile

improve helpfile by adding subcategories and clarifying usage.
improve UTILITY category part of help
Merge pull request #79 from tphyahoo/develop-helpfile

Develop helpfile