Add reference packages for several commonly used SMD transistor packages

[p12tic]

• Created a new library for transistor packages. Named it ref-packages-transistor.lbr.
• Copied packages from ref-packages-eagle.lbr library.
• Verified the packages to corresponding JEDEC standards.
• Changed the outlines on tPlace and tDocu layers to match the outline specified in the standard. This was not the case in most cases. Now the lines are drawn according to the nominal outline and its width almost matches the tolerances as specified in the standard.
• Synchronized the new packages throughout all libraries. Manual verification has been done in all cases. Multiple variants of single package with different solder footprints were used throughout the libraries inconsistently, thus the consolidation has led to slight changes to packages in lots of cases.
• The obsolete reference packages were removed.

The following are the names of the added packages:
SOT223
SOT23-6
SOT23-5
SOT23
SC70-6
SC70-5
SC70-3