updated static db: students and execrise.
add new future: lecture to add new execrise.
Fixed classes: Course, Execrise
fix wrong usage of classes
create exec.
Merge pull request #69 from aglos/sharon2

Sharon2
Fixed classes (still need fixed).
create edit page to checked execrise and read data from db.
add future - now the lecturer adding new exericse.
Working on table checker page and lecturer page.
Pushing students array into the grade scales.
Added new DB records for: execrises and studnts and students grades.
marking on checker table - check/ not checked exericse.
loding and showing graph data from the db
Merge pull request #70 from aglos/sharon2

Fixed classes (still need fixed).
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fixed classes