one-button builds

It is finally possible to build and package Psi, with dependencies, using a 
single command. At the moment this only works for Mac, but it will soon work 
for Windows as well.

  export QTDIR=/path/to/qt
  cd admin/build && make VERSION=somestring

With the exception of Qt (which you're assumed to have, and you must set 
QTDIR), this will automatically download all other dependencies prior to 
compiling. Notably you no longer have to hand-edit version strings in files. 
Files containing version numbers are generated.

Most of the dependency packages are downloaded from psi-im.org [1]. What's 
nice is many of these packages are generally built in a similar one-button 
fashion via scripts from the psideps repo.

Everything is being built as 32-bit + 64-bit x86. For Mac, a universal binary 
is made. For Windows, there will be two packages, one for each arch. Minimum 
OS targets are Mac 10.5 and Windows XP.

What's left: psimedia package for Windows, and then Psi itself for Windows. 
Once this is done, I'll be restoring the daily snapshots and putting out 0.15-
beta2.

At some point I also want to script the Windows installer, but generally we 
have not used installers for daily snapshots or betas, so this won't be a 
blocker.

Justin