Added frontend tag functionality

Tags are now visible for blog posts and projects. Clicking on a tag will
relist the blog posts/projects, filtering out the ones without a
matching tag.

Changes:
* controllers/blog.php ~ added function tag which handles displaying
blog posts matching a selected tag
* core/MY_Model.php ~ fixed issue with getSubsidiaryData call. It was
not properly determining whether the sql result was an object.
* helpers/view_processing_helper.php ~  Added two functions for working
with tag strings and tag slugs. Also carried over an improvement from
tag building to vp_buildArticleSlug: added line to replace + in article
titles with plus.
* models/blogpost_m.php ~ added functions for retrieving/counting blog
posts by tag.
* views/project/project_detail_v.php ~ Added tags to project detail
* views/template/blog_post_v.php ~ Added tags to blog post
* controllers/project.php ~ added functions for filter projects by tag
* models/project_m.php ~ added functions for retrieving/counting
projects by tag
* views/blog/blog_index_v.php ~ removed hr from between blog posts
* views/contact/contact_V.php ~ removed contact notice...its only going
to provoke spam!
* views/project/project_preview_v.php ~ replaced local image path
$imgDir with the one defined in the frontend controller $imageDir.
* css/main.css ~ added bottom margin to blog posts