webos-filesystem-paths: Add pre-installed catalog apps location

:Release Notes:
Add the location of the IPKs for the pre-installed catalog apps:
webos_picapkgdir.

:Detailed Notes:

:Testing Performed:
The output from
  $ make BBFLAGS=-e cjson | grep 'export webos_picapkgdir'
shows that the variable has been set correctly.

:QA Notes:

:Build Notes:
This commit invalidates all shared state.

:Issues Addressed:
[GF-40846] Add support for building pre-installed catalog apps (PICA)

Open-webOS-DCO-1.0-Signed-off-by: Herb Kuta <herb.kuta@lge.com>
Change-Id: Ie133bcd67bc22db68c93027f2f0d65023f5d7d4c
Reviewed-on: https://g2g.palm.com/3609
Tested-by: Herb Kuta <herb.kuta@lge.com>
Reviewed-by: Build Verification
Reviewed-by: Keith Derrick <keith.derrick@lge.com>
Reviewed-by: Herb Kuta <herb.kuta@lge.com>