fix PDESystem REPL (#1181)

Author: KirillZubov

src/systems/abstractsystem.jl

@@ -183,8 +183,8 @@ for prop in [
              :loss
              :bcs
              :domain
-             :depvars
-             :indvars
+             :ivs
+             :dvs
              :connection_type
              :preface
             ]

src/systems/pde/pdesystem.jl

@@ -85,8 +85,8 @@ function Base.show(io::IO, ::MIME"text/plain", sys::PDESystem)
     println(io,"Equations: ", get_eqs(sys))
     println(io,"Boundary Conditions: ", get_bcs(sys))
     println(io,"Domain: ", get_domain(sys))
-    println(io,"Dependent Variables: ", get_depvars(sys))
-    println(io,"Independent Variables: ", get_indvars(sys))
+    println(io,"Dependent Variables: ", get_dvs(sys))
+    println(io,"Independent Variables: ", get_ivs(sys))
     println(io,"Parameters: ", get_ps(sys))
     print(io,"Default Parameter Values", get_defaults(sys))
     return nothing