fix GlassEditFrame constructor and its usage - it makes no sense to create this class without writer

- add writer to GlassEditFrame(EditFrame frame) constructor, it makes no
sense and produces incomplete object (=with no writer) that would fail
in Dispose method
- remove workaround for this in  BeginEditFrame(this HtmlHelper
htmlHelper, EditFrame editFrame) html helper
fix - map/load Guid.Empty to Sitecore fields as String.Empty (instead of {0000...})

fix - map/load Guid.Empty to Sitecore fields as String.Empty (instead of
{0000...} - it breaks our code when loading back (we don't know what is
empty and what is really  guid with all zeroes) and  also when saving
item back - it saves zeroed guid to fields instead of empty string
allow parent attribute to be mapped also to types Guid and Sitecore.Data.ID

allow parent attribute to be mapped also to types Guid and
Sitecore.Data.ID - previously it can be mapped only to object
fix loading assemblies when HttpContext.Current == null (background threads)

- use HttpRuntime.AppDomainAppPath when http context is not defined (=
when using Glass in background threads - Sitecore 7 computed fields in
search index)
- not sure why bin path is used for assembly loading  -
Assembly.Load(assemblyName); seems to work too and does not need to
resolve bin folder at all - alternative code added as comment
MakeEditable<T> - run field renderer also when standardOutput is null

run field renderer also when standardOutput is null, otherwise
link/image fields are shown only in page editor when using Editable
our custom info attributes

HasVersion - True if item has a version. The property type must be bool
HasLock - True if current user has a lock on the item
Created -  Gets the creation date of the item
Updated -  Get the date of the latest update to the item