Changing the name of forms classes

We think the name that we put in forms elements was very confusing. The
label was called .ls-field and the text of label was called ls-field.
Now, we chage this to this:
label is **.ls-label**
text of label is **.ls-label-text**
input/field is **.ls-field**
fieldset or another form container is **.ls-form-group**

We think this is better.