Update Model.php function asDateTime: startofDay(00:00:00) if from Y-m-d timestamp (DateAccessor)

As the pull request https://github.com/laravel/framework/pull/2227 was closed but the startOfDay() was only inserted in the function fromDateTime, this pull request adds startOfDay() also to the accessor function (asDateTime), so you can compare two dates without the automatically added incorrect time of the current moment.
Shorter syntax use && for and use || for or
Remove special SQLite order by logic.
Resolve conflicts.
Merge pull request #2578 from lanort/4commit

Update Model.php function asDateTime: startofDay(00:00:00) if from Y-m-d...
Merge.
Many "use" statements are useless and can then be safely removed
Convert to new bindShared method on container.
Merge pull request #2585 from semalead/use-removal

Unnecessary "use"
Fix MySQL unions with parens.