Backport of fix #31 from 1.6 branch
Fix upgrade bugs. Hope this will definitely get rid of them.
Should fix #30
Merge pull request #33 from dethegeek/1.5-bugfixes

1.5 bugfixes
Merge branch '1.6'

Merge 1.6 branch into master
merge branch 1.6 into master
Fix uninstall : glpi_plugin_customfields was not deleted when during
uninstall process

Add a comment about some code which needs a review
Fix #36 : install wrong database version in install process. The object
budget
is created, and when clicking on the activate button un GLPI, the
upgrade takes place and created the same object again.
Update es_ES.php

Translation of $LANG['plugin_customfields']['setup'][1]
Merge pull request #37 from slopneal/patch-2

Update es_ES.php
Fix reading the database version mark. Sometimes there are several
version marks although there should be only one.

should help fix #35
Update README.md
Update README.md
Update authors of the plugin
Restrict usage of the plugin on GLPI 0.84.x
Create dummy method to ensure compatibility with other plugins which
create new itemtypes (plugin simcard). Will be filled to acutally handle
these new item types.
restore simcard plugin compatibility. This was a regression due to all
code changes done while forking and porting the plugin to GLPI 0.84
Merge branch 'master' of https://github.com/dethegeek/customfields

merging changes on readme.md and WIP on new features
computerVirtualMachine may have custom fields
Split install and upgrade into 2 functions