File clean up.

Four files removed: sqlite/db_*.php
All non-sqlite app files removed
Path to SQLite database updated
Files from sqlite/ moved one level up
HDF logo's location updated
icesat2.css renamed to hpd.css
More extraneous files removed
style.css removed
Code clean up
Merge branch 'feature-sqlite-only' into develop
Fixed HPD-37 issue.

Dataset now shows attributes that are linked.
Attribute search filter is fixed.
Merge remote-tracking branch 'origin/develop-HPD-37' into develop
Merge branch 'release-0.3'