conversion output shapes can be different when using broadcastable inputs

[gregstarr]

Describe the bug Depending on which conversion is being performed, if you use inputs with the intent to array-broadcast, you can get mismatched output shapes. See: https://github.com/aburrell/apexpy/pull/27#issue-552468596

To Reproduce Steps to reproduce the behavior:

1. create arrays for lat, lon and time
2. perform a geo to mlt conversion with each input extended along a different dimension
3. examine output shapes

Expected behavior The output arrays should have the same shape, instead, because mlat doesn't depend on time, it will only be size 1 along the time dimension.

apexpy version: develop

[aburrell]

Other methods that have trouble with broadcasting issues are:

• basevectors_apex
• basevectors_qd
• map_E_to_height
• map_V_to_height