better docs for AliasSpecifiers

Author: jClugstor

docs/src/interfaces/Common_Keywords.md

@@ -101,9 +101,12 @@ Note that if a method does not have adaptivity, the following rules apply:
 
 ## Memory Optimizations
 
-  - `alias`: an `ODEAliases` object that holds the field `alias_u0`, which allows the solver to alias the 
-    initial condition array that is contained in the problem struct. For example, tell the solver to alias `u0`,
-    `solve(prob,alias = ODEAliases(alias_u0 = true))`. Defaults to `ODEAliases(alias_u0 = false)`.
+  - `alias`: an `AbstractAliasSpecifier` object that holds fields specifying which variables to alias
+    when solving. For example, to tell an ODE solver to alias the `u0` array, you can use an `ODEAliases` object, 
+    and the `alias_u0` keyword argument, e.g. `solve(prob,alias = ODEAliases(alias_u0 = true))`. The fields of 
+    every `AbstractAliasSpecifier` default to `nothing`, which tells the solver to use its default behavior. 
+    For more information on what can be aliased for each problem type, see the documentation for the `AbstractAliasSpecifier`
+    associated with that problem type. 
   - `cache`: pass a solver cache to decrease the construction time. This is not implemented
     for any of the problem interfaces at this moment.