Mkw issue 105

[mwalte10]

Most of this diff are changes that were implemented in mkw_issue_101

The substantive changes are regarding how maternal PMTCT dropout are implemented. A summary:

• Postnatal Option A and Option B use dropout rates for mothers on PMTCT, not the option A and B dropout rates in the spectrum editor
• Spectrum was recently updated to not allow women on ART to transmit more than once. I track this in this intermediate variable: intermediate.children.previous_mtct.

Once this is merged I will continue to stratify new infections by maternal ART use

[mwalte10]

@r-ash @M-Kusumgar do you guys know why the windows-latest is failing here?