Split inferWriterDriver into two

Similar to #340, the 2-argument infer{Reader|Writer}Driver might try to
do too much by both modifying options and finding the correct driver.
This patch splits the inferWriterDriver into two pieces. The
inferWriterDriver part does just that, while a new method,
inferWriterOptionsChanges, modifies an options object based upon a given
filename.
Merge pull request #341 from gadomski/feature/split-infer-writer-driver

Split inferWriterDriver into two
Merge StageBase into Stage.
Merge pull request #344 from PDAL/no-stage-base

Merge StageBase into Stage.
add decimation option to pdal translate
Merge pull request #345 from chambbj/issues/43-pdal-translate-decimation

add decimation option to pdal translate for #43
Merge branch 'master' of github.com:PDAL/PDAL into issues/339-remove-interleaving
remove user-specific config scripts into cmake/examples to clean up root directory #342
Merge pull request #342 from PDAL/issues/342-no-more-top-level-config.sh

Remove personal configuration scripts
Merge branch 'master' into issues/339-remove-interleaving