Add gvm_auto_{install,use} in $GVM_DIR/etc/config

Fixes #101.

These flags are consulted when gvm is asked to use an uninstalled version
or to install an unused version.  User is prompted for a response
by default but this can be overridden by adding these flags to
the confg, e.g.

$ echo gvm_auto_install=Y >> $GVM_DIR/etc/config
$ echo gvm_auto_use=Y >> $GVM_DIR/etc/config
$ gvm use groovy 1.8.8
... (installs and uses without prompting)
Merge pull request #119 from dsyer/master

Trivial changes to .gitignore
Use a single flag 'gvm_auto' instead of separate use/install
Rename auto var to gvm_auto_answer
Merge pull request #118 from dsyer/feature/autoinstall

Add gvm_auto_{install,use} in $GVM_DIR/etc/config
Minor tweaks to auto install configuration and cukes.
Upgrade feature renamed to Self Update.
Adds configuration of auto answer on install and selfupdate.
Rename upgrade steps to selfupdate steps.
Upgrade to cucumber-jvm 1.1.1
Updating vertx install command.
Merge pull request #124 from greymeister/fix-readme

Updating vertx install command.