Add tags support

Set slugify to be global
Update modification date only if text has been changed
Fix a bug in preview (post_id was passed instead of blog_id)
Add Home, Category and Tag links in blog area instead of global area (dynastie template)
Fix a bug in Have_I_right

forms.py

@@ -1,4 +1,5 @@
 from django.forms import ModelForm
+from django import forms
 from dynastie.models import *
 
 class BlogForm(ModelForm):
@@ -6,6 +7,10 @@ class BlogForm(ModelForm):
         model = Blog
 
 class PostForm(ModelForm):
+    description = forms.CharField(widget=forms.Textarea(attrs={'rows':'5', 'cols':'50'}), required=False)
+    keywords = forms.CharField(widget=forms.Textarea(attrs={'rows':'2', 'cols':'50'}), required=False)
+    text_tags = forms.CharField(widget=forms.Textarea(attrs={'rows':'2', 'cols':'50'}), required=False)
+
     class Meta:
         model = Post
         exclude = ('title_slug', 'creation_date', 'modification_date', 'author', 'blog', 'tags')
@@ -28,3 +33,8 @@ class CommentForm(ModelForm):
     class Meta:
         model = Comment
         exclude = ('post', 'parent', 'date')
+
+class TagForm(ModelForm):
+    class Meta:
+        model = Tag
+        exclude = ('blog', 'name_slug')