Add named patterns

[varkor]

A constructor like Siteswap.parse that accepts both siteswap notation as well as natural-language names like 5-ball cascade would be very useful. This will likely entail coming up with a canonical naming scheme for juggling patterns.

[varkor]

5847004 goes some way to adding this, but there are a few families of named siteswaps that are currently unsupported (as they either rely on a recursive notation for siteswap families, or repeated sections — see #14).
Some named siteswaps that are currently unsupported:

• Alternating shower (<{2n-1}2>^{n-2}{2n-1}12, where <> represent groups)
• Box (({4n-8}, 2x)...* where ... represents a recursion)
• Freezeframe ({2n-1}...)
• Snake (<{2n-1}0>^{n-1}{2n-1})
• Half-shower (both this and the psuedo-shower have multiple possible patterns for a given cardinality, so it is unclear which to pick)
• Pseudo-shower