Fixing initial status issue

[bknueven]

Fixes # .

Summary/Motivation:

If the uptime/downtime provided is fractional, Egret may not enforce the initial on/off time correctly. The new tiny_uc_12.json demonstrates the issue:

min_up_time: 2.2
initial_status: 1

Currently, the formulation allows a decommitment in the 2nd hour using an hourly horizon, e.g, [1,0,...] is an acceptable schedule. The bug fix and new test ensure this isn't permitted.

Changes proposed in this PR:

• Change inappropriate round to math.ceil for InitialTimePeriodsOffLine and InitialTimePeriodsOnLine.
• When a ModelData object is serialized, create the directory the user specifies if it doesn't exist.

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