I reimplemented everything according to the new plan. Here is what we have:

• The standard DECam linearity table is in the decam dir
• scons builds LSST linearizers from the DECam linearity table. This required adding decam/SConscript and minor changes to SConstruct and tests/SConscript (so tests don't run until the linearizers are available)
• I added decam/README.md to explain the new files. It should be updated to explain some of the other files, but I don't have that information.
• Updated the DECam camera mapper to look for linearizers in the new location. Note that the information is no longer in the .paf file.

There are no changes to testdata_decam or ip_isr but branches with no changes exist in order to pacify the CI system.

Hsin-Fang Chiang would you be willing to have another look? I think it is fully cleaned up, and it passes Jenkins CI.

Looks fine to me. I'm a bit confused that in some places the directory "decam/linearizer" is hard-coded, in other places it relies on DecamMapper.getLinearizerDir(). Maybe that's necessary because scons needs it?

Thank you for reviewing the code again. I am also uncomfortable hard-coding the path to the LSST linearizers in scons build files, but it turns out that it is neither easy nor safe to import LSST code into an scons build file (unsafe because we cannot assume that scons and our code use the same python interpreter, and we may even end up with scons running python 2 and our code requiring python 3). So hard-coding the path in the build files appears to be a pragmatic choice, though far from ideal.

merged to master