Add unary operator support for profiles

[Zetison]

This PR provides unary operator support (for + and -) for profiles.

This basic functionality is convenient for example if one wants to model a market node in EMX as done here. One is then enabled to write

power = ResourceCarrier("Power", 0.0)
prices = [[10, 60, 15, 62], [9, 59, 14, 61]]
price_profile = StrategicProfile([OperationalProfile(p) for p in prices])
market_sale = RefSink(
    "market_sale", 
    FixedProfile(0), 
    Dict(
        :surplus => -price_profile,
        :deficit => price_profile
    ),
    Dict(power => 1), 
)

which simplifies code and abstracts away a call to the profile constructor compared to

power = ResourceCarrier("Power", 0.0)
prices = [[10, 60, 15, 62], [9, 59, 14, 61]]
market_sale = RefSink(
    "market_sale", 
    FixedProfile(0), 
    Dict(
        :surplus => StrategicProfile([OperationalProfile(-p) for p in prices])
        :deficit => StrategicProfile([OperationalProfile(p) for p in prices])
    ),
    Dict(power => 1),  
)

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Files with missing lines	Coverage Δ
src/profiles.jl	84.93% <100.00%> (+5.88%)	⬆️

... and 7 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[JulStraus]

I am not opposed to it. Formatting should be however done.

[trulsf]

Looks good to me