Updates to support read/write of additional INP sections

[kaklise]

I have been using swmmio to add stormwater/wastewater analysis to WNTR. The ability to read, modify, and write INP files using pandas DataFrames has been very helpful! I found a few issues when comparing simulation results with and without the read/write of INP files ([XSECTIONS], [INFLOWS], and [CURVES]). I also needed to support a few additional sections in Model.inp ([CONTROLS] and [PATTERNS]). I stored controls and patterns in DataFrames with 1 line per entry. I'm using INP files from SWMM and swmmio to test functionality. Let me know if you're interested in a PR!

[aerispaha]

@kaklise, I'm so happy that swmmio has been helpful for you. 100% we're interested in a PR! Please feel free to submit a PR at your convenience, then we can continue the conversation there :)