Adds cmdline switch to specify ftpdata section

When working on feature branches for uploading to a testing server
using the branch name as section from the ftpdata file is not
helpful. The new commandline switch allows manual selection of the
appropriate section from the ftpdata file.

Example: git-ftp.py --section development

Uses ftpdata section 'development' regardless of the active branch
name.
Merge pull request #68 from dl1ely/7970c4536ad583d1b0745a4430f7b19d0cd20cb1

Allow overriding of section name in ftpdata file from commandline