allow obsid dubplicates by introducing another ID as primary key

[jkall]

Introduce a unique observation id that is independent of obsid and name. This will allow the existance of duplicates among obsid.

Major code revisions are needed. Several security checks are needed during imports and also, when obsid duplicates are found, user interaction to distinguish between observations of same obsid.

Probably time to introduce a main table with id for each observation as the primary key. This table will hold all observations, no matter if they are points or lines.