Integrals in Integrals are the same size now

Signed-off-by: bvanr <henkibrij@hotmail.com>
Created the ShowcaseViewDialog class to make ShowcaseView work for our DialogFragments

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
Merge remote-tracking branch 'bas/basbranch3' into work
The logarithm's base now defaults to 10, fixes #135

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
The zoom level is now reset when deleting the expression (fixes #138)