[write] be strict with dims area

[JanMarvin]

Currently when providing dims to write data, we should provide an option to check if the area we are writing to is equal to dims and otherwise we should inform the user, maybe even abort if they don't match. Something like this:

• user writes 4 x 4 matrix into single cell. error
  • user writes 4 x 4 matrix into 2 x 4 cell. optional warning
  • user writes 4 x 4 matrix into 4 x 2 cell. optional warning
• user writes 1 cell to 4 x 4 matrix. optional warning

In a second attempt we should respect the user requested cells. If dims "A1:D1;B2:E2" is requested, only these cells should be filled.

This should include #37.